Consumers use paper wiping products, such as facial tissues and bath tissues, for a wide variety of applications. Facial tissues are not only used for nose care but, in addition to other uses, can also be used as a general wiping product. Consequently, there are many different types of tissue products currently commercially available.
In some applications, tissue products are treated with polysiloxane lotions in order to increase the softness of the facial tissue. Adding silicone compositions to a facial tissue can impart improved softness to the tissue while maintaining the tissue""s strength and while reducing the amount of lint produced by the tissue during use.
In the papermaking industry, various manufacturing techniques have been specifically designed to produce paper products which consumers find appealing. Manufacturers have employed various methods to apply chemical additives, such as silicone compositions, to the surface of a tissue web. Currently, one method of applying chemicals to the surface of a tissue web is the Rotogravure printing process. A Rotogravure printing process utilizes printing rollers to transfer chemicals onto a substrate. Chemical emulsions that are applied to webs using the Rotogravure printing process typically require the addition of water, surfactants, and/or solvents in order for the emulsions to be printed onto the substrate. Such additions are not only costly but also increase drying time and add process complexity.
Another method of applying chemical additives to the surface of a tissue web is spray atomization. Spray atomization is the process of combining a chemical with a pressurized gas to form small droplets that are directed onto a substrate, such as paper. One problem posed with atomization processes is that manufacturers often find it difficult to control the amount of chemical that is applied to a paper ply. Thus, a frequent problem with spray atomization techniques is that a large amount of over-spray is generated, which undesirably builds upon machinery as well as the surfaces of equipment and products in the vicinity of the spray atomizer. Furthermore, over-spray wastes the chemical being applied, and comprises a generally inefficient method of applying additives to a tissue web. Additionally, lack of control over the spray atomization technique also affects the uniformity of application to the tissue web.
In view of the above, a need exists in the industry for improving the method for application of chemical additives to the surface of a paper web.
In general, the present invention is directed to an improved process for applying compositions to paper webs, such as tissue webs, paper towels and wipers. The present invention is also directed to improved paper products made from the process.
For example, in one embodiment, the present invention is directed to a process for applying an additive to a paper web, such as a tissue web, that includes the step of extruding a viscous composition onto the paper web. The viscous composition has a viscosity sufficient for the composition to form fibers as the compositions is extruded onto the web. In general, any suitable extrusion device can be used to apply the composition to the web. In one embodiment, for instance, the composition is extruded through a melt blown die and attenuated prior to being applied to the web.
The composition can generally be any material that provides benefits to paper webs. For instance, the composition can be a topical preparation that improves the physical properties of the web, that provides the web with anti-bacterial properties, that provides the web with medicinal properties, or that provides any other type of wellness benefits to a user of the paper web. For instance, the composition can contain an anti-acne agent, an anti-microbial agent, an anti-fungal agent, an antiseptic, an antioxidant, a cosmetic astringent, a drug astringent, an aiological agent, an emollient, an external analgesic, a humectant, a moisturizing agent, a skin conditioning agent, a skin exfoliating agent, a sunscreen agent, and mixtures thereof. In one embodiment, the composition is a softener. The softener can be, for instance, a polysiloxane.
Of particular advantage, the process of the present invention is well-suited to applying relatively high viscous compositions to paper webs. For instance, the process can have a viscosity of at least 1000 cps, particularly 2000 cps and more particularly can have a viscosity of at least 3000 cps. Since the process is capable of handling high viscosity compositions, various chemical additives can be added directly to a paper web without having to dilute the additive with, for instance, water or any other type of dilution agent to form a solution or emulsion.
In fact, in one embodiment, a thickener can be added to the composition in order to increase the viscosity. The thickener can be, for instance, a polyethylene oxide. It should be understood, however, that any suitable or conventional thickener can also be used.
The amount of the composition that is applied to the paper web depends on the particular application. For example, when applying a softener to a tissue web, the softener can be added in an amount from about 0.1% to about 10% by weight and particularly from about 0.1% to about 5% by weight, based upon the weight of the web. As described above, in one embodiment, the composition is extruded through a melt blown die onto the paper web. The melt blown die can have a plurality of nozzles at a die tip. The nozzles can be arranged in one or more rows along the die tip. The fibers exiting the nozzles can have a diameter of from generally about 5 microns to about 100 microns or greater.
The process of the present invention provides great control over the amount of composition applied to the web and the placement of the composition on the web. It is believed that products made according to the process of the present invention have various unique characteristics. For instance, in one embodiment, a product made according to the present invention includes a paper web containing cellulosic fibers. The viscous composition containing a chemical additive is applied to at least one side of the paper web. In accordance with the present invention, the composition is present on the paper web in the form of fibers, such as continuous filaments.
In some applications, depending upon the composition that is applied to the paper web, a paper web treated in accordance with the present invention will have improved strength characteristics, particularly an improved cross direction wet:dry ratio. For instance, when treating a paper web in accordance with the present invention, the cross direction wet:dry ratio can increase by at least 25%, particularly at least 40%, and more particularly by at least 50%. For example, a tissue web treated with a hydrophobic composition, such as a polysiloxane, can have a wet:dry ratio of at least 0.45, particularly at least 0.48, and more particularly at least 0.52.
Various features and aspects of the present invention will be made apparent from the following detailed description.